Fluid pressure system



Jan. 23, 1945. s. SCHNELL FLUID PRESSURE SYSTEM Filed May 23, 1942 FlG.l.

L ML TE NN H mx a 'ir ATTORNEY Patented Jan. 23, 1945 UNITED STATES PATENT OFFICE FLUID PRESSURE SYSTEM Steve Schnell, Kirkwood, Mo., assignor to Wagner Electric Corporation, St. Louis, Mo., a corporation of Delaware Application May 23, 1942, Serial No. 444,175

14 Claims.

' employed to obtain all required actuating pressures.

Yet another object of my invention is to so embody a pump in a pedal-controlled hydraulic actuating system that in the event of failure of the pump, the system can, nevertheless, be efflciently operated by actuation of the pedal.

Still another and more general object of my invention is to produce an improved fluid pressure actuating system embodying a pump which enables the operator to properly control the actuating pressure under all conditions and by a manual force which is proportional to the actuating pressure.

Another object of my invention is to provide in a fluid pressure system an improved pump and control means therefor.

Other objects of my invention will become apparent from the following description taken in connection with the accompanying drawing in which Figure 1 is a schematic view of a braking system embodying my invention; Figure 2 is a broken sectional view showing details of the power driven pump associated with the system; and Figure 3 is a sectional view of one reciprocating piston and valve structure of the pump.

Referring in detail to the drawing and first to Figure 1, numeral i indicates a master cylinder device which comprises a cylinder 2 having reciprocable therein a piston 3, said piston being actuated by a piston rod it and a pedal 5. The

piston 3 is normally biased to its inoperative position by a return spring 6 and when in this position, it uncovers a compensating port l for placing the cylinder ahead of the piston in com munication with the reservoir 8. The outlet of the master cylinder is connected by conduits 9 and it and branch conduits l l to fluid motors l2. These fluid motors may be employed to actuate any devices desired and by way of example, said devices are shown as brakes i3. interposed between conduits s and it is my improved combined pump and control means therefore generally indicated by the numeral I4 and shown in ,detail in Figures 2 and 3. This pump and control means is so associated with conduits 9 and I0 that the operation of the pump can be controlled by fluid pressure developed by the master cylinder device so that a predetermined greater fluid pressure can be caused to be effective in the fluid motors l2. The control arrangement is also such that in the event the pump fails to become operative, the fluid pressure'de'veloped by the master cylinder will be effective in the fluid motors.

Referring in detail to Figures 2 and 3, the combined pump and control means is embodied in two connected casings l5 and It, the former being provided with two chambers i1 and I8 which are to be filled with the same operating fluid as that in the master cylinder device. These chambers I1 and ii! are connected with reservoir 8 of the master cylinder by a conduit l9. Thus when chambers l1 and I8 are filled, reservoir 8 will also be fllled. A shaft 20 is mounted in suitable hearings in casing I5 and extends to the exterior of the casing where it has secured thereto a pulley 2| for belt connection with a suitable source of power, as, for example, an internal combustion engine of a vehicle. The inner end of shaft 20 projects into chamber l8 and has rotatably mounted thereon a roller 22, the axis of which is at right angles to the axis of the shaft. The inner end of the shaft is also so formed as to have a counter-balancing portion 23 opposite the roller 22.

The other casing It has a bore formed to provide axially aligned connecting cylinders 24 and 25 of difierent diameters. Slidable in these cylinders is a two-diameter piston 26. The end of the large cylinder is connected to conduit 9 leading to the master cylinder device, thus permitting the large end of piston 26 to be subject to the fluid pressure which is developed by the master cylinder device. I The smaller end of the twodiameter piston carries a pin 21. which extends into chamber l8 and pivotally mounted thereon by a ball and socket connection is a swash plate 28 which cooperates with roller 22 carried on shaft 20.

Casing i6 is also provided with four reciprocating pumps generally indicated by the numeral 29, said pumps being positioned in surrounding relation to the axis of piston 26 and having their parallel axes equally spaced with respect to each other. In the sectional view shown in Figure 2 only two of these pumps are shown as the section is taken on such a line that the other two are cut away. Each of these pumps is mounted within a bore 30 and, as shown in Figure 3, the bore receives a cylindrical member-8| in which is reciprocably mounted a piston 32 connected to the swash plate by a ball and socket connection 33. The piston has a passage 34 permitting fluid to enter the compressing chamber 36 ahead of the piston and this passage is controlled by an intermediate reduced portion of piston 26.

In addition to the bore which is provided with cylinders 24 and 25, casing I6 is also provided with a second bore formed to provide cylinders 43 and 44 of difierent diameters. The larger cylinder 43 communicates with the end of cylinder 25 and the connected conduit 8 by means of a passage 45 and the end of the smaller cylinder 43 is connected with conduit I leading to the fluid motors I 2. Within cylinders 43 and 44 is a two-diameter piston 46 having a passage 41 therethrough. The smaller end of this piston is provided with a valve portion 48 for cooperation with a seat 49 for preventing communication through the passage 41. The valve. element 48 is normally held seated by a. spring 58. The piston 46 carries two packing elements and 52 arranged to prevent passage of fluid past the piston in either direction.

The piston 26 is provided with packing cups 63 and 54, said packing cups being so arranged that fluid in chamber 42 surrounding the central portion of the piston cannot pass either end of the piston. However, fluid is capable of passing the large end of piston 26 to enter chamber 42 by the collapsing of the lip of cup 53. In order to facilitate this passage of fluid, the large end of piston 26 is provided with openings 55. The chamber 42 communicates with conduit to leading to the fluid motors by a passage 56 entering the end of the small cylinder 44.

In the particular construction shown the twodiameter piston 26 is so constructed that the fluid pressure present in chamber 42 must be approximately twice that of the fluid pressure acting on the large end of the piston before the piston 26 can be moved to the left. Also, the twodiameter piston 46 is so constructed that the large end of the piston has an area substantially twice that of the small and of the piston. The piston 46 will thus be held in the position shown where valve element 48 is seated as long as the fluid pressure. acting on the large end of the piston is substantially half of that acting on the small piston and tending to move the piston to the left.

Referring now to the operation of my improved fluid pressure system, the entire system is first completely filled with a suitable operating liquid. The shaft 28 of the pump which may be constantly driven will not cause any pumping action when the master cylinder is in its released condition as the swash plate 28 will be in a vertical plane as shown andv the roller 22 will merely rotate on the surface of the swash plate. Should it be desired to apply fluid pres-,

sure to the brakes, the brake pedal 5 is actuated. This will result in port 1 being closed and fluid pressure developed by piston 3. This fluid pressure will be transmitted through conduit 8 and into the large cylinders 25 and 43. The fluid pressure acting on the large end of piston 46 will hold the element 48 seated. The fluid pres sure acting on the large end of piston 26 will move this piston to the right and thereby'cause the pivoted center of the swash plate to be moved toward the end of shaft 20. Some fluid entering the large cylinder 25 under a normal operation of the master cylinder device will probably pass cup 53 and the large end of the piston and enter chamber 24 where it will be transmitted to the fluid motors, thus causing the brake shoes to start to be brought into engagement with their drums. If the master cylinder device should be very rapidly operated, then more fluid under pressure will pass cup 53. As soon as the swash plate has been tilted by the movement of piston 26, the rotation of shaft 20 will cause the swash plate to be actuated in a well-known manner, thereby progressively reciprocating the pistons 32. Due to the valve elements associated with the pumps, the pistons will force fluid under pressure into chamber 42 which will be added to that already transmitted to the fluid motors.

When the fluid pressure developed by the operation of the reciprocating pistons reaches a value which is substantially twice the pressure which has been developed by the master cylinder device, piston 26 will be moved to the left and thus return to its position shown in Figure 2.

At this point pumping will cease because the pivoted center of the swash plate again reaches such a position that the swash plate will be vertical to the axis of shaft 28 and the roller merely rolls around the end surface of said swash plate. It is thus seen that if, for example, the master cylinder has been caused to develop fifty pounds per square inch of pressure, this flfty pounds of pressure will be immediately eflective in the system and as a result of development of such pressure, the pump will be caused to operate. The pump will then place the fluid pressure effective in the fluid motors under a pressure of one hundred pounds per square inch. When this pressure is reached, the pump will cease pumping. This increasing of fluid pressure in the fluid motors during pump operation will not, however,

cause any increase in pedal pressure over that necessary to develop th fifty pounds per square inch. If it should be desired to increase the pressure in the fluid motor, additional movement of the master cylinder pedal is all that is necessary. The fluid pressure developed by this additional movement of the pedal will again move the piston 26 to the right and thereby cause operation of the pumps to such an extent that these pumps will develop additional pressure in the fluid motors l2 until such pressure is twice that developed by the master cylinder.

When it is desired to release the brakes, all that is necessary is to release the pedal 5. As soon as the fluid pressure in the master cylinder begins to decrease, there will be a decrease in the fluid pressure effective on the large end of piston 46. This decrease will result in the fluid pressure acting on the small end to move piston 46 to the left and thereby unseat the element 48. The central passage through the piston is now open and fluid can return to the master cylinder. The excess fluid which has been placed in the system by the operation of the pump will pass out through the compensating port I of the master cylinder device and into the reservoir where it can return to chambers l8 and I1 associated with the pump. If it is desired to only release a portion of the fluid pressure which is effective in the fluid motors, the pedal need only be permitted to partially return. This will result in the lowering of the pressure acting on the large end of piston 46 and cause the valve element 48 to be unseated. The valve element, however, will again be seated as soon as sufllcient pressure is relieved so that the pressure acting on the large end of the piston is half that of the pressure acting on the small end of the piston.

In the event the pump should fail to operate, there will be no failure of the system, The fluid pressure which can be developed in the motors will, however, only be that developed by the master cylinder device. The piston 26 can have only a limited movement toward shaft 20. Before release of fluid pressure in the fluid motors, the pressure developed by the master cylinder will have to be decreased to approximately one-half that developed.

Although there has been shown and described a structure whereby the fluid pressure developed by the pump and effective in the fluid motors is twice that of the pressure developed by the master cylinder, it is obvious that any ratio between these two pressures may be obtained by merely changing the ratios between the various areas of the tw pistons 26 and 46 which are acted upon by fluid under pressure.

Being aware of the possibility of modifications in the particular structure herein described without departing from the fundamental principles of my invention, I do not intend that its scope be limited except as set forth by the appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

i. In a fluid pressure actuating system, a source of fluid pressure, a device to be actuated by fluid under pressure, a fluid pressure pump having its outlet communicating with the device to be actuated, a power driven member for driving the pump, means comprising a movable member controlled by fluid pressure from the source for causing said pump to be driven by the power driven member and establish pumping operation but only for a sufficient interval of time to place the fluid in said device under a proportionally greater pressure than the pressure from the source, and means associated with said movable member for permitting the fluid pressure from the source to be efiective in the device when the pump is inoperative to develop a greater pressure.

2. In a fluid pressure actuating system, a master cylinder device, a fluid motor, a power driven fluid pressure pump having its outlet communicating with the motor, a reservoir for the pump, means controlled by fluid pressure developed by the master cylinder device to cause said pump to develop a fluid pressure effective in the motor which is proportionally greater than that developed by the master cylinder device, means for permitting fluid pressure developed by the master cylinder to be transmitted to the motor when the pump is not effective to cause a greater fluid pressure in said motor, means independent of the last two named means and comprising a movable member having different areas exposed to the fluid pressure from the master cylinder and that eflective in the motor for releasing the fluid pressure in the motor to the master cylinder, and

means for returning fluid from the master cylinder device to the pump reservoir.

3. In a fluid pressure actuating system, a source of manually-controlled variable fluid pressure, a. fluid motor, a fluid pressure pump having a check valve-controlled outlet communicating with the motor for injecting fluid under pressure into said motor, a power driven member for the pump, means comprising a movable member connected to a control element of the pump and having positions where the pump is either caused to be operated or not operated by the power driven member, said member being provided with an area subject to the fluid pressure from the source for moving the member to a pump operating position and another smaller area subject to the fluid pressure developed by the pump for returning the member to a position where the pump ceases its pumping, and means for releasing the fluid pressure from the motor and returning it to the source.

4. In a fluid pressure actuating system, a master cylinder device, a fluid motor, a fluid pressure pump having a check valve-controlled outlet communicating with the motor for injecting fluid under pressure into said motor, a power driven member for mechanically operating said pump,

means comprising a movable member having positions where the pump is either operated or not operated by the power driven member, means for moving the member to a pump operating position by fluid pressure developed by the master cylinder device, means for moving the member to a position where the pump ceases its pumping when the pump develops such a higher pressure in the motor that a predetermined ratio exists between the master cylinder developed pressure and the motor pressure, and means for supplying fluid pressure to the motor from the master cylinder device in the event the pump does not operate to develop a higher pressure.

5. In a fluid pressure actuating system, a source of manually-controlled variable fluid pressure, a fluid motor, a power driven fluid pressure pump having its outlet communicating with the motor, means controlled by fluid pressure from the source for causing said pump to develop a fluid pressure effective in the motor which is proportionally greater than that from the source, and means operable by a decrease in the pressure of the source for permitting a return of fluid to the source to thereby decrease the fluid pressure in the motor.

6. In a fluid pressure actuating system, a master cylinder device, a fluid motor, a power driven fluid pressure pump having its outlet communicating with the motor, mean controlled by fluid pressure developed by the master cylinder device to cause said pump to develop a fluid pressure effective in the motor which is proportionally greater than that developed by the master cylinder device, and other means operable by a decrease in pressure being developed by the mastercylinder for permitting a. return of fluid to the master cylinder and thereby decrease the fluid pressure in the motor, said last named means maintaining the same proportion between the pressure being developed by the master cylinder and that effective in the motor as that which was present at the beginning of the decrease.

7. In a fluid pressure actuating system, a source of fluid pressure, means for varying at will the fluid pressure from the source, a fluid actuated motor, a power driven fluid pressure pump having its outlet communicating with the motor, means controlled by fluid pressure from the source to cause the fluid pressure pump to operate and develop fluid under pressure in the motor, means for causing said pump to be inoperative when the pressure developed thereby is such that a predetermined ratio exists between the pressure from the source and the pressure in the motor, and other means comprising a member operable by a decrease in pressure of the fluid pressure from the source for releasing fluid pressure from the motor.

8. In a fluid pressure actuating system, a master cylinder device, means for operating the device to develop and decrease fluid pressure at will, a fluid motor, a power driven fluid pressure pump having its outlet communicating with the motor, means controlled by fluid pressure developed by the master cylinder device to cause aid pump to develop a fluid pressure eiiective in the motor which is proportionally greater than that developed by the master cylinder device, means for permitting fluid pressure developed by the master cylinder to be transmitted to the motor when thepump is not effective to cause a greater fluid pressure in said motor, and other means operable by a decrease in pressure being developed by the master cylinder for decreasing the fluid pressure in the motor.

9. In a fluid pressure actuating system, a master cylinder device, a fluid motor, a fluid pressure pump having its outlet communicating with the motor, mean comprising a movable member for controlling the operativeness of the pump, means for moving the member to a pump operating position by fluid pressure developed by the master cylinder device, means for moving the member to a pump inoperative position when the pump develops such a pressure in the motor that a predetermined ratio exists between the master cylinder developed pressure and the motor pressure, and means comprising a second movable member for permitting the fluid under pressure in the motor to be released when the fluid pressure being developed by the master cylinder device is released.

10. In a fluid pressure actuating system, a source of pressure, a fluid motor, a fluid pressure pump having its outlet communicating with the motor, means comprisin a movable member for controlling the operativeness and inoperativeness of the pump, said member being provided with an area subject to the fluid pressure from the source for moving the member to a pump operating position and another smaller area subject to the fluid pressure developed by the pump for returning the member to a position where the pump is inoperative, means for permitting fluid under pressure to flow from the source to the motor when the pressure from the source is greater than that in the motor, and means comprising a second movable member permitting fluid under pressure to be released from the motor whenever the fluid pressure from the source is so decreased below the pressure in the motor that the ratio determined by the areas on said first member no longer exists between the pressures of the source and motor.

11. In a fluid pressure system, a pump having an outlet, said pump being of the reciprocating piston type provided with a swash plate actuating means for operating the pistons of the pump, a movable member, means for mounting the central part of the swash plate for universal pivotal movement on said member, an actuating member for said swash plate having an element for engaging the peripheral portion of the swash plate on the side opposite the operated pistons and rotatable in a fixed circular path, and means for moving said movable member to thereby move the pivot of the swash plate relatively to the element of the actuating member to thus vary the operating angle of the plane of the swash plate with respect to the axis of the actuating member.

12. In a fluid pressure system, a pump having an outlet, said pump being or the reciprocating piston type provided with a swash plate actuating means for operating the pistons of the pump, an axially movable member, means for mounting the central part of the swash plate for universal pivotal movement on said member, a rotatable haft axially aligned with the movable member and having an element movable in a fixed circular path and engageable with the peripheral portion of the swash plate, said shaft and movable member being independently mounted, manually controlled means for moving said member in one direction to cause pump operation, and means for moving the member in the opposite direction by fluid pressure developed by the pump to cause the pump to become inoperative.

13. In a fluid pressure system, a pump having an outlet, said pump being of the reciprocating piston type provided with a swash plate actuating means for operating the pistons of the pump, a movable member, means for mountin the central part of the swash plate for universal pivotal movement on said member, means for moving said movable member to thereby move the pivot of the swash plate relatively to the element of the actuating member to thus vary the operating angle of the plane of the swash plate with respect to the axis of the actuating member. a source of variable fluid pressure independent of the pump, means for moving the movable member in one direction by fluid pressure from the source, and means for moving the member in the opposite direction by fluid pressure developed by the pump.

14. In a fluid pressure system. a pump having an outlet, said pump being of the reciprocating piston type provided with a swash plate actuating means for operating the piston of the pump, a movable member, means for mounting the central part of the swash plate for universal pivotal movement on said member, an actuating member for said swash plate having an element for engaging the peripheral portion of the swash plate and rotatable in a fixed circular path, means for moving said movable member to thereby move the pivot of the swash plate relatively to the element of the actuating member to thus vary the operating angle of the plane of the swash plate with respect to the axis of the actuating member, a source of variable fluid pressure independent of the pump means for moving the movable member in one direction by fluid pressure from the source and comprising an area on the movable member subject to the fluid pressure from the source, and means for moving the member in the opposite direction by fluid pressure developed by the pump and comprising an area on the movable member smaller than the first named area and subject to the pump developed pressure.

STEVE SCHNELL. 

